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Selasa, 12 November 2013

Self Tapping Screws And Other Magical Devices

By Bonnie Contreras


Another name for self tapping screws is self drilling screws. The clue is in the name. They drill the hole in the metal for you so you do not have to drill what is called a pilot hole first. This is useful when you want to mount things like computer monitors onto metal shelving because you do not have to fiddle around matching up holes, you just drill the screw through everything and you only have to do it once.

They are brilliant gadgets and well loved by those who use them. They save marriages, spare injuries and involve a lot less hair-pulling and swearing. That almost takes the fun out of it. They are also used to mount surveillance cameras on a metal frame and in dentistry. Tooth implants are considered to be self tapping screws.

Like other screws, the heads of the self tapping kind are either plain or cross-headed. The cross-headed, or Phillips, variety give a little extra stability when juggling two or more layers of material. It is amazing how a trivial difference in structure can make a huge difference in function. It really is a matter of having the correct tool for the task at hand.

Most screws have a right-handed, or clockwise, thread. To tighten, turn clockwise; to loosen, turn counter-clockwise. The easy way to remember this is righty-tighty, lefty-loosey. The same mnemonic works for opening and closing jars as well as adjusting the radiator.

There are a wide variety of screw types. The distance between threads along the shaft, for example, is called the pitch. The metal from which they are made is also a factor; this can be steel, zinc, copper, nickel, brass or chromium. They can have flat or round heads and one or two grooves in the head. The ones with two grooves that are at right angles to each other are called Phillips head or cross head screws.

The design for the Phillips head screwdriver was purchased from its inventor, John Thompson, from a man from Portland Oregon named Henry Phillips. Phillips made a few tweaks and then had the final design patented. Among its early users was the firm that manufactured the Cadillac, General Motors. Phillips eventually sold the patent to the Ford Motor Company for a grand total of $5 million, an enormous sum now and even more enormous in 1945.

When a screw is likely to face strong counterclockwise torque, which would loosen a right-handed screw, a left-handed screw is the correct choice. For instance, the left side of a bicycle has a left-handed thread. Anything with helical threads can legitimately be called a screw. The propeller of a ship is an example, as is an Archimedes' screw water pump.

Self tapping screws are brilliant devices that save time and hassle when fastening pieces of metal to one another without the need to drill separate holes which you then have to fiddle around and line up. Sometimes, less is more when it comes to design. Screws have a lot of different varieties. They are made from a number of different metallic materials, such as copper, chromium, steel, zinc or nickel.




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